The present invention relates to an electrophotographic system comprising an electrophotographic copier and an option device for forming an enlarged or reduced image of a document set in the option device or accessory.
The copying apparatus represented by an electrophotographic copier has been used in many ways for the purpose of copying documents, and almost all of the copiers are constructed to obtain a life-size copy of the same document being copied. On the other hand, there are known copiers that print a reduced image of a large size document or an enlarged image of a microfilm in an electrophotographic manner, but such apparatus is assembled in a copier as an inseparable form, or in case of using it as an option device, use is made of the same optical path as that of the copier itself or use is made of a part of an optical path in common with copier. It is a common technique to assemble a reduction optical system in the copier itself inseparably, but the thus assembled apparatus becomes large and complicated. It is further known to detachably add an optical image projector to the copier itself as an option or accessory device, but such apparatus also has various defects. For example, in Japanese Patent Application Publication No. 4,944/67, Japanese Patent Application Publication No. 8,437/69, Japanese Patent Laid-open No. 62,724/76, Japanese Utility Model Laid-open No. 127,827/77, Japanese Patent Laid-open No. 55,647/77 and the like, there is disclosed that the whole frame of a microfilm image is projected on a document table or a photosensitive member as a still picture by an option device and the projected image is scanned and exposed in the former apparatus by a scanning optical system, while in the latter apparatus the projected image is directly converted into an electrostatic latent image. However, the copier for copying the whole frame of a microfilm image projected as a still picture is as large as the apparatus itself and lacks universality and convenience as compared with the copier of the document moving, scanning and exposing type which has recently been widely used. In the former system for projecting the microfilm image on the document table, when an enlarged image is projected by an option device, it is necessary to provide a long optical path in the device, so that the option device becomes disadvantageously large.
Further, in copending U.S. Patent Application Ser. No. 261,740, there is disclosed a duplicating system comprising an electrophotographic copier of the slit exposure and scanning type in which the document to be copied is moved at a given constant speed with respect to a scanning optical system and an option device also of the slit exposure and scanning type.
This duplicating system comprises an electrophotographic copying apparatus which includes first optical scanning means for making a slit exposure, first means for feeding a first document to be copied at a first speed with respect to said first optical scanning means, photosensitive means for forming an electrostatic latent image corresponding to the image of the document, and means for forming a duplicated copy with the aid of said latent image, and an option device which includes means for detachably mounting the option device into the copying apparatus, second optical scanning means for making a slit exposure, second means for feeding a second document to be copied at a second speed with respect to said second optical scanning means, and optional optical means for projecting the image of the second document onto said photosensitive means of the copying apparatus; wherein said second optical scanning means in the option device is so constructed that the image of the second document is projected onto the photosensitive means through an optical path which passes through entrance and exit points of said first optical scanning means, but does not include the first optical scanning means.
In this duplicating system, since the image of the second document fed in the option device is projected onto the photosensitive means at the same position at which the image of the first document fed in the copying apparatus is projected, it is not necesary at all to modify a sequence control device provided in the copying apparatus. Therefore, the duplicating operation by means of the copying apparatus and the option device is simple, and further the copying apparatus and option device can be manufactured easily.
In the duplicating system of the kind mentioned above, it is preferable to provide document detecting devices such as microswitches and photoelectric switch at the document insertion ports of both the copying apparatus and the option device, thereby automatically starting the duplication for a detected document. However, after a first document has been detected by one of the detecting devices and a duplicating operation for the first document has been started, when a second document is detected by the other detecting device, the second document will also be fed and scanned. Therefore, a correct duplication could not be effected. In order to avoid this the second document must be inserted into the duplicating system after the duplication for the first document has been completed, but this imposes inconvenience and difficulty upon a user. The above mentioned drawback may be removed by modifying the control sequence, but such a solution results in a complicated sequence control and conflicts with the above described advantage obtained by providing the optical scanning means in both the copying apparatus and the option device so as to control them under the common sequence control.